Bridge for diaphragm violins



Patented Dec. 8, 1925.

UNITED STATESv LEMA@ PATENT FFIQE.

GLENN D. BOTHWELL, 0F SPRINGPORT, MICHIGAN, ASSIGNOR OF ONE-THIRD TO GUY J'. IBOTHWELL, OF LONDON, ONTARIO, CANADA. f

BRIDGE FOR DIAPHRAGM VIOLINS.

Application filed February 26, 1923.

To all Iwhom t may concern.'

Be it known that I, GLENN D. Bori-rwnLL, a citizen of the United States, residing at Springport, in the county of Jackson and State of Michigan, have invented a new and useful Bridge for Diaphragm Violins, of which the following is a specification.

Yibis invention relates to stringed musical instruments and particularly relates to string supporting bridges for such instruments.

It is the object of the invention to provide a. string-supportiug bridge adapted to freely respond to the vibrations of the supported strings and to provide supporting means for said bridge adapted to transmit such vibrations to the diaphragm elem-ent of the shell or sound-box of the instrument across which the strings are extended.

In attaining this object, the invention contemplates employing an intermediately pivoted lever, one extremity of which is adapted to support the string-bridge while the other extremity of said lever is connected to the diaphragm element of a sound-box, preferably centrally of said element, said bridge being adapted to pivotally vibrate about its other end to actuate said lever and transmit vibratory movement to said diaphragm element.

A preferred embodiment of theinvention is hereinafter described, and is illustrated in the accompanying drawing, wherein,

Fig. 1 is a view in side elevation of a stringed instrument improved in accordance with the invention.

Fig. 2 is a longitudinal sectional view of the same.

F ig. 8 is a transverse sectional view, taken on line 3-3 of Fig. 2.

In these views, the reference character 1 designates the strings of a musical instrument and 2 the body shell or sound-box across which said strings are extended. Said sound-box comprises a bottom board 3, the top face of which is routed out to form a cavity of suitable proportions to serve as the sound-box chamber, and i is a top-board marginally secured to the board 3 and suiiiciently thin to serve as a diaphragm for the sound-box. 5 is a substantially rigid bridge member which transversely spa-ns the sound- -bon seating upon opposite margins of the same. The string-supporting bridge 6 cenj'trally surmounts the bridge 5, the ends of Serial No. 621,270.

the former respectively engaging a vertical flexible post 7 and a lever S mounted upon the latter. Said post is rigidly anchored at the lower end in a groove 9 in the bridge 5, and the bridge 6 is' formed in its lower edge with a V-shaped notch engaging said post.

rlhe lever 8 passes freely through a slot 10 inthe bridge 5 and has its lower end rigidly secured to the diaphragm 4, preferably at the center of the latter, by a screw 8. The upper end of said lever is pointed as indicated at 11 and seats in a V-shaped notch in the corresponding end of the bridge 6. Below the point 1l, and within the slot 10, the lever S .is pivoted upon a pin 12 mounted transversely in the bridge 5. The lever 8 is laterally bent, just above the pivot pin l2, to establish the desired off-set relation of the point 11 and pin 12 with relation to the central point of the diaphragm 4s, which is the point of attachment of the lever, the intermediate portion of the lever being reduced in thickness to render it iiexible. By virtue of this olf-set relation, vibratory pivotal movement of the lever upon said pin is applied to the diaphragm at an acute angle to the plane thereof. This motion is resolved into com ponents respectively transverse to and parallel with the diaphragm, the former acting to vibrate the diaphragm and the latter being absorbed by flexing of the intermediate portion of said lever. The sound vibrations of the air within the sound-box are adapted to be emitted through a central opening 13 in the member 3, which opening is in communication with the restricted end of a horn 11i through a passage 15, these features however being more especially the subject-matter of my copending application filed Feb. 26, 1923. Serial Number 621272.

When one or more of the strings 1 are set in vibration, by application of a bow or by other means for agitating said strings, the resulting vibrations are directly communi cated to the bridge 6, which has a limited freedom of movement for response to such vibration. The vibrating of the bridge 6 has the nature of a bodily lateral movement, the post 7 iiexing to permit such movement. The upper end of the lever 8, owing to its engagement in the notch of thebridge 6, is moved laterally in unison withthe bridge, thus causing a pivotal vibration of said lever uponjthe pin 12 as a fulcruin member. Flexure ofthe lower portion of the lever acts The eii'eet of transmitting the. vibrations of the strings to the diaphragm o1 the soundbox by a lever or equivalent solid element is to considerably intensify the emitted sound vibrations as compared to an instrument 1n which the air is required to transmit the vif brations of the strings to the sound-box.

That I` claim is 1. In a stringed instrument, a soundbox having a diaphragm, strings extending aorossfsaid' sound-box, al bridgel supporting:

saidv strings adjacent said diaphragm, aflexible" support for one'end of said bridge, per@ mitting. vibratoryv movement of the latter, andi al` support for the opposite" endv of said bridge pivotal about an axis substantially parallel to the strings and engaged Withsaid diaphragm to impart to the latter the vibrations of said bridge. y

2. ln a stringed instrument, a soundbox having a diaphragm, strings extending across.` said sound-box, a stationary bridge spanning said diaphragm, a vibratory bridge supporting said strings, a flexible support interposed between said. stationary and vibrat'ory bridges, and a vibrator7 lever pivotally interposed between said stationary and vibrator-y rbridges and lixedly engaged with said diaphragn'i to Subject the latter to the vibrations of said vibratory bridge.

In testimony whereof I sign this specification'.

GLENN n. BOTH'WELL. 

